Welcome to part four of _On the brain, a Conversation series by people whose job it is to know as much as there is to know about the body’s most complex organ. Here, Neil Levy, Head of Neuroethics at Florey Neuroscience Institutes, considers the role of “choice” and “responsibility” in addictive behaviour. Enjoy._

Public discussions of addiction too often fall into the trap of simplistic slogans.

One side asserts addicts are fully responsible for what they do and can choose to act differently; the other side asserts addiction is a brain disease and that therefore addicts do not choose their behaviour.

Both views are partially true, but each is also very misleading. Addicts do make choices, including the choice to consume the drug to which they are addicted. But the neuropsychological changes involved in addiction mean their capacity for choice is abnormal enough to mean it would often be unreasonable to expect them to make alternative choices.

You choose

What is it to make a choice? Roughly speaking, we choose when we respond to reasons. A reflex is not a choice: when the doctor hits my kneecap, I don’t respond to a reason to jerk my leg.

A behaviour that looks more like a choice – compulsive hand-washing, say – might not be a choice if it is not responsive to reasons.

We test to see whether the behaviour is responsive to reasons by seeing how the person responds to various incentives. If the person is choosing, they will make a different choice given the right incentive.

So the compulsive hand-washer is choosing to wash her hands if she would stop for $100, or because she is hungry (enough), or what have you.

Ms. Tina

Using this test, it’s immediately apparent that addicts make choices, both to engage in activities (sometimes illegal, of course) to procure their drug, and to consume their drug.

An addict would not shoot up, for instance, were they sitting opposite a police officer. Their behaviour is sensitive to reasons, and therefore is chosen.

But as the example of the compulsive hand-washer illustrates, saying a piece of behaviour is “chosen” is only the beginning of the story. Sufferers from obsessive-compulsive disorders, phobias and so on, make choices, but their choices are pathological in various ways.

We can see this using precisely the same kind of test we used to show they are making choices at all. Take the person who suffers from agoraphobia – fear of open spaces – and who therefore does not leave their house for months or even years. We can show they are choosing to remain inside by showing they would go out were they presented with a sufficiently large incentive.

By the same token, the fact they would not go out for a smaller incentive shows their choices are severely constrained. An agoraphobic might leave his house if he ran out of food entirely, but not, say, if all he had left was spaghetti, or merely to avoid severe social embarrassment. These facts show his choices are highly abnormal.

And the fact he would not leave the house to avoid a moderate harm, or to gain a moderate benefit (say to get $500) helps us to see it would be unreasonable to expect him to make alternative choices under the circumstances in which he finds himself.

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A great escape

The evidence with regard to addiction seems to indicate addicts’ choices are similarly constrained. Due to a variety of factors, addicts find it far harder to control some of their actions then most other people.

Neuroadaptations (whereby the brain attempts to compensate for something that influences normal functioning) decrease the control these people have over their actions, and also make drugs and drug-related cues hard to ignore.

Very often this, when added to concurrent mental illness, poverty and hopelessness, makes a drug-facilitated temporary escape very tempting. In other words, they choose, but they find it harder to make alternative choices.

These facts often make it unreasonable for us to expect addicts to make better choices. Whether it’s unreasonable on a particular occasion depends on what the choice is.

We rightly expect people to try harder to avoid seriously immoral actions, such as mugging a stranger, then less serious. The more distant the relationship between the addiction and the action, the less difficult addicts typically find it to exercise control.

So we might reasonably expect addicts to avoid mugging strangers for money to buy heroin, but it might be unreasonable to expect them to refrain from taking the drug when they have it. Again, it will depend on the circumstances.

We might expect more of an addict who becomes a mother (and the evidence suggests parenthood often does provide a sufficient incentive to many addicts to stay clean).

We need to give up simplistic dichotomies such as “chosen” or “responsible”. We need to recognise human action exists on a continuum, on which a great deal of behaviour is chosen but to different degrees.

And we need to develop means of assisting addicts so they can make better choices.

That means adopting a multi-pronged approach in which we address all the circumstances that make their choices difficult.

This is the fourth part of our series On the brain. To read the other instalments, follow the links below: